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Raptor E325 › tail bounce - any ideas to fix
10-11-2011 10:40 AM  7 years agoPost 1
imf

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UK

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I have a Mini Titan with a GY520. Does not matter where I set the gain percentage 20% or 70% the tail still bounces when I stop a pirouette and that not a fast pirouette.

Servo ball is set to 7.5mm centre, gyro mounted on one piece of 2mm foam pad (as recommended in instructions, rudder endpoint set to 100%, Gyro set to F3c mode and fast response (but was the same when set to standard response). Absolutely no tail mechanism binding.

Any ideas?

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10-12-2011 08:33 AM  7 years agoPost 2
scottward

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Brisbane, Australia

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Check tail servo on the bench.

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10-12-2011 10:35 AM  7 years agoPost 3
punkin71

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illinois

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I have read that a rate mode set up for the gy 520 helps with this but havent tried it yet. my gy520 bounces like this but only in 1 direction, cant remember which, it did this when mounted on my trex 500 and still does it my mini titan!

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10-12-2011 12:31 PM  7 years agoPost 4
gwright

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Champaign Il

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Change the servo arm to a much longer arm,..I'd start with 12~13mm, then adjust the gain until there is no wag. You're looking to get it down to around 30 to 40%. If it's still above 50 or so, lengthen the arm again. Once you get it with no wag and around 40% or maybe a little below (while in AVCS), then go to rate mode and adjust the linkage mechanically to trim it very close to no movement, then switch back to AVCS mode. At this point you should go back into the gyro setup and adjust the endpoints again for no binding. Adjust ATV or AFR in your transmitter to get the desired maximum spin rate. (I prefer AFR as it leaves the trim sensitivity alone).Now, if there is any rebound on stops you can increase the stop delay a point or two at a time to eliminate it. I'm not sure which transmitter you use, but with the 14MZ I actually prefer to set the stop delay in the transmitter,..it's on the AFR screen as "servo-out delay". It's irrelevant if you do it in the gyro or the transmitter, I simply prefer the transmitter as it's quicker to make adjustments since you don't have to stop the blades and go into the gyro setup.
The issue is the speed of reaction which is increased by lengthening the servo arm. It basically speeds up the entire system so it doesn't get behind on the corrections and allow the rebound. One key rule of thumb with the 520 is to get the gain down below 50 , preferably in the 30's, which indicates the arm is long enough.
I just went through this on the X50-E. I've been unhappy with the tail setup but was concentrating on power system, gearing, pitch and left it alone till now. I think the arm I ended up with is around 16mm or so and it took less than a single flight to do all of the above stated setup to get the tail absolutely rock solid.

Gary Wright

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10-12-2011 02:51 PM  7 years agoPost 5
imf

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UK

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Thanks for the replies.

Gary,

I will try lengthening the horn and report back. The servo I have fitted on the MT is a 9257. I have a 520 with 9254 on my 500 and 600 and there is no bounce what so ever and they have 13mm ball centres on the servo horns.

Meanwhile I've been trying different things and got it to a minimum but it is still there when stopping from quite fast piros to the left. I set the 520 to 3d mode and the 'responce rate' to slow (although the instructions say this is for larger helicopters). I put up the end points to 130% with 20% expo (softening) on rudder and it feels really nice, better than it has ever been with the GY401 - very progressive but powerful and holds like a rock.
My headspeed of 3400rpm in idle up and a max gain of 43% in AVCS (any higher and the bounce increases)and 70% in rate mode.

I always do the mechanical setup in rate mode and there is zero drift. There is no binding either way.

You say you can adjust the piro rate using AFR. I have a T7C (pretty basic) and as far as I know the only AFR setting is the Swash AFR. As for 'stop delay' I do not have this either. You say it can be adjusted in the gyro, which setting is that, Parameter 5? If so there are only 3 settings so less adjustment than it sounds like you have on the 14MZ.

IMF

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10-12-2011 03:31 PM  7 years agoPost 6
gwright

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Champaign Il

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AFR is basically the same as ATV (adjusts travel volume of the servo), however it does not affect trim rate. I'm not sure of the exact numbers, but for the sake of explanation lets say the trim will move the servo 20% of the total movement. If you cut ATV down to 50% you halve the movement of the servo with stick inputs plus the movement with trim inputs (it's 20% of the 50% that you decreased total travel to). With AFR, you get the same result with the actual stick input, but you retain the same trim amount,..not percentage. In this example, the trim would then be 40% of the total movement. The difference being that trim volume is unaffected with AFR. It's only a minor difference, but I like trim sensativity to remain the same since I run different AFR's in different flight conditions.

It sounds like you only need to adjust the stop delays. I don't think that that is available in the 7C, so just do it in the gyro. to do this in the 520 you need to use the CIU2 interface and the free software that's downloadable from the futaba site. There are many paramaters that can be adjusted with this that are not available by simply pressing the button on the gyro. The one you would want to adjust is the AVCS response. The software allows you to fine tune the in and out delays independantly, and left and right independantly.

http://www.futaba-rc.com/software-updates.html and you want "GY520 Gyro Software". Page 8 of the pdf manual shows a screenshot of the available options you may tune.

Gary Wright

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10-12-2011 05:56 PM  7 years agoPost 7
Skaluf

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Champaign, IL

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I agree with Gary, your setup sounds fine. Adjust the Stop Delay and you will be in fat city. You'll find you like the adjustability the GYLink software gives the GY520.

Of course, if you are in the market for a new transmitter; the 18MZ has this software built into it.

Steve

Steve Kaluf
Hobbico

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10-19-2011 11:50 PM  7 years agoPost 8
imf

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UK

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Thanks again Gary for that information I'll order a CIU2 tomorrow.

--------------

Steve,
I have not had time to try a longer servo horn as Gary suggested. You said my setup sounded fine, is that with the 7.5mm ball centre or do you recommend I try Gary's suggestion of 12 to 13mm ball centre?

18MZ sounds lovely but too many switches for me

-------------

IMF

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10-20-2011 10:53 PM  7 years agoPost 9
imf

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UK

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Changed the servo horn from 7.5mm to 13mm today and was able to set the 520 parameters back to F3c mode and standard response. The gain is set to 32% and the rudder end point is 140. On very quick stops to the right I still get a bounce but not too bad.

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10-20-2011 11:26 PM  7 years agoPost 10
gwright

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Champaign Il

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good, sounds like there's some improvement. With the gain in the proper range and the servo arm longer I would bet it probably holds better overall too.

Gary Wright

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10-21-2011 12:05 PM  7 years agoPost 11
imf

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UK

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Yes it holds well. I'm looking forward to getting the CIU2, my supplier is out of stock for a couple of weeks. I'll report back when I have made the adjustments.

Would you think that the possible flex in the standard wire pitch change wire would cause the bounce?

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10-21-2011 12:24 PM  7 years agoPost 12
gwright

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Champaign Il

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that's highly unlikely. Just needs some delay in the stop. What that effectively does is slow the servo's return to neutral, like if you just moved the stick back to center a little slower rather than letting it slam back to neutral. This lets the deceleration from yaw occur smoother so it doesn't get the sharp stop that leads to the bounce

Gary Wright

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10-23-2011 05:47 PM  7 years agoPost 13
imf

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UK

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That all makes sense Gary because if I do a hard piro and just cushion the stick when I return it to centre it does not bounce. I suppose it is doing what the 'Delay' setting on the 401 does but.

I have made no adjustments on the 520's on my trex500 and trex 600, I suppose some tails can handle it better then others.

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